An effective approach to single and multi-axis linear and angular position determining systems has been shown in U.S. Pat. No. 4,035,762, issued on July 12, 1977 to Jacques R. Chamuel. Such patent describes various embodiments for measuring a position along a line, either straight or curved, or on a plane, a sphere, or other curvilinear surface, with a high degree of accuracy at a reasonable cost. In many of the embodiments described therein a delay line element, preferably fabricated of a magnetostrictive material, has a driver transducer which is utilized to produce a traveling wave which travels along the magnetostrictive delay line, the presence of which wave is subsequently detected by a receiver transducer. The receiver transducer, for example, may be movable with respect to the delay line and to the driver transducer which is fixedly positioned for coupling to the delay line. By appropriate phase shift measurements utilizing continuous wave signals or by suitable time delay measurements utilizing pulse signals, as described therein, linear or angular positions can be accurately determined with a high degree of resolution.
As discussed in the above-referenced Chamuel patent, when using a delay line element, the ends of the delay line are terminated in appropriate energy absorbing materials so as to prevent signal reflections thereat. The presence of such reflections tends to affect the linearity of the phase modulation of the C-W signals in the positioning determining measurement and, if the energy at the ends of the line can be sufficiently absorbed so as to reduce reflections to negligible levels, the linearity in most applications is satisfactory.
In some applications, however, the presence of even relatively small reflections may be sufficient to reduce the linearity of the measurements to a point where the device becomes much less effective than is required for the particular use to which it is being put. It is desirable, therefore, to improve such linearity by preventing the effects of reflections from introducing a nonlinear response in the operation of the device.